Process of purifying cyclopentadienyl nickel nitrosyl compounds



United States. Patent 3,067,227 PROCESS OF PURIFYING CYCLOPENTADIENYL NICKEL NITRQSYL COMPOUNDS William R. Axtell, J. Byron Bingeman, and Albert P.

Giraitis, Baton Rouge, La., assignors to Ethyl Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 8, 1959, Ser. No. 845,086 2 Claims. (Cl. 260-439) This invention relates to a process for producing organo-nickel compounds and more particularly to a novel process for recovering cyclopentadienyl nickel nitrosyl compounds from impure reaction products containing the same.

cyclopentadienyl nickel nitrosyl compounds have been found to be very effective antiknocks for gasoline, used in internal combustion engines. One preferred method of manufacture of these compounds involves a three-step process: (1) reaction of an alkali metal with a cyclopentadiene hydrocarbon; (2) reaction of nickel chloride with the cyclopentadienyl alkali metal compound formed in Step 1; and (3) reaction of the bis(cyclopentadienyl) nickel compound formed in Step 2 with nitric oxide. All of the above steps are conducted in an ether or amine solvent.

The above process steps are usually carried out sequentially, without separation of by-products. Thus, the cyclopentadienyl nickel nitrosyl compounds are obtained in a crude' reaction mixture with large quantities of inorganic salt, organic dimers and other polymers and minor quantities of various organo nickel derivatives. The high polymers and salt can be separated from the more volatile compounds, including the desired product, by'distillation, e.g. vacuum or steam distillation. Ho ever, rectification of the volatile fraction of the crude product requires a large number of separate steps and results in considerable operational difficulty.

This. volatile fraction of the crude reaction mixture contains cyclopentadiene polymer (primarily dimer), solvent, and volatile organo nickel compounds including the desired cyclopentadienyl nickel nitrosyl compound. In addition, the volatile fraction usuallycontains a relative- 1y high boiling hydrocarbon such as an aromatic com? poundwhich is effectively used as a suspending agent to aid in the initial removal of the inorganic impurities and the high polymers. Most of the suspending agent is separated With the impuritiesbutsmall quantities frequently carry over with the volatileproducts and require separation, e.g. fractionation from the desired product.

In either batch or continuous distillation, considerable difficulty is encountered due to decomposition of various components in the above impure product. The polymer, although relatively high boiling, tends to decompose below its boiling temperature and results in frothing'and generally unpredictable process conditions during fractionation of the various components. Moreover, it is virtually impossible to obtain a clean separation of components since during fractionation, these relatively high boilingcomponents of the reaction mixture decompose resulting in the formation of much lower boiling components such as cyclopentadiene monomer which upsets the condition infractioning columns or other separation equipment.

It is accordingly anobject. of this invention to provide an improved process for recovery of cyclopentadienyl nickel nitrosyl compounds. Another object ,is to provide a recovery process which'is readily adaptable to large scale commercial operation and permits efiicient separation of'the various components of the mixture and very efficient control of the process. Still another object is to provide a recovery 'process whereby the cyclopenta dienyl nickel nitrosyl compound can be recovered in especially high yields and purity with a minimum of process steps. Still another object is to provide a process 1n which the components such as solvent and unreacted .cyclopentadiene compound can be recovered essentially free of the cyclopentadienyl nickel nitrosyl so as to permit recycle to the process without materially poisoning the reaction. Other objects and advantages of this invention will become more apparent from the following description and appended claims.

It has now been found that the impure reaction mixture containing a cyclopentadienyl nickel nitrosyl product can be stabilized to permit simple and eflicient fractionation of its components if the mixture is initially subjected to elevated temperatures, i.e. above about 160 C. and preferably above about 200 C. for a period sufiicient to decompose unstable components of the reaction mixture. It has been found that this thermal treatment can be conducted to selectively decompose undesired components while still not decomposing the desired cyclopentadienyl nickel nitrosyl product. Following such thermal decomposition, the resulting impure mixture-can then be fractionated or otherwise separated-without con tinued. decomposition, thus permitting eflicient and com plete fractionation of the diiferent components of the mixture. V

More specifically the process of this invention is use: ful in separating a cyclopentadienyl nickel nitrosyl compound from an impure reaction product containing the same and also containing quantities of unreacted cycloe pentadiene hydrocarbon compound in polymeric form, comprising subjecting the impure product to a tempera? ture of above about 160 C. and preferably above about 200 C. for a period of time, suflicient to depolymerize the cyclopentadiene compound and thermally stabilizethe reaction product and thereafter fractionating the stabi lized reaction productto separate the cyclopentadiene compound from the cyclopentadienyl nickel nitrosyl com pound.

The chemical steps of the process normally employa solvent, usually an ether or an amine, Whichit is neces; sary to separate and recover from the. product. With low boiling solvents, such as diethylether, this. separation can be conducted prior to the thermal treatment by simplev distillation. With higher boiling solvents, such as with the preferred diethylene glycol lower, dialkyl-ether solvents, e.g., diethylene glycol dimethyl ether, diethylene glycol diethylether and other homologs containing alkyl groups having 1 to 3 carbon atoms, the solvent separa tion can be conductedsimultaneously with the thermal treatment or with still higher boiling solvents, i.e..solvents boiling higher than the product, suchas, when .diethylene glycol dibutyl ether. is. used in the. manufacture of methylcyclopentadienyl nickel nitrosyl, the solvent canbe. removed after the thermal treatment.

In a preferredembodiment of this invention, the thermal treatment is carried out simultaneously with fractionation of .one .or more .of thevolatile components, such as thesolvent or cyclopentadiene compound-or both. Thus, this distillation-can be conducted under sufiicient pressure to maintain the distillation temperature above the desired thermal decomposition temperature, i.e. 160 C; to simultaneouslystabilize. the mixture and separate certain of its components. Simultaneous separation of both the solvent and cyclopentadiene compound is particularly desirable since both can be recycled to the process. and separation prior to recycle is usually unnecessary. However, it is usually desirable' todimerize the cyclopentadiene compound, e.g. cyclopentadiene: or methylcyclopentadiene, prior to recycle ifrelatively high temperatures, i.e. 'above C. are employed in th e sodium reaction. This substantially reduces the reactiv- 3 ity of the hydrocarbon with sodium and avoids an unduly violent reaction.

It is also found that in using the process of this invention, the solvent and cyclopentadiene compound are surprisingly free of product, thus making recycle directly to the process possible without poisoning the chemical reactions.

The benefits of the present process are particularly surprising and unexpected. It is very unusual to be able to heat an organometallic compound, particularly an organonickel compound, to such high temperatures, even in the presence of impurities which would normally be expected to catalyze decomposition. Moreover, the present recovery process is capable of providing much sharper separations of the reaction components than has been heretofore thought possible. The present technique eliminates frothing in the fractionation operations, especially in continuous operations which has previously seriously interfered with the necessary separations and in some cases made fractionation impossible.

A wide variety of cyclopentadienyl nickel nitrosyl compounds can be recovered by the process of this invention. In general, any nickel nitrosyl compound containing a molecule including the 5 carbon atom ring structure found in cyclopentadiene itself is suitable for recovery by the process of this invention. The process is particularly suitable for compounds containing a cyclopentadienyl group having 5 to 13 carbon atoms. Typical examples of compounds which can be recovered by the process of this invention are cyclopentadienyl nickel nitrosyl, methylcyclopentadienyl nickel nitrosyl, ethylcyclopentadienyl nickel nitrosyl, dirnethylcyclopentadienyl nickel nitrosyl, n-decyl cyclopentadienyl nickel nitrosyl, phenylcyclopentadienyl nickel nitrosyl, methylphenylcyclopentadienyl nickel nitrosyl, indenyl nickel nitrosyl, fluorenyl nickel nitrosyl, and the like.

The impure reaction products which can be treated in accordance with this invention contain both the cyclopentadienyl nickel nitrosyl compound and unreacted cyclopent'adiene hydrocarbon, primarily in polymeric form, e.g'. dimeric form. This reaction product is produced from any of the presently known processes for manufacture of these compounds. The cyclopentadiene hydrocarbon polymer results in most instances both from unreacted monomer, which subsequently polymerizes, and from cy'clopentadienyl radicals freed during reaction of bis(cyclopentadienyl) compounds with nitric oxide, forming the corresponding mono-cyclopentadienyl nickel nitrosy=l compound.

The residence time of the thermal stabilizing treatment varies depending upon the temperature employed and the particular cyclopentadienyl compound involved. In other words, higher temperatures and less stable polymers require shorter period of thermal treatment. Normally, the impure reaction mixture is maintained at a temperature above 160 C. for a period of at least one minute, and usually for a period of at least minutes to insure complete stabilizing of the mixture. This treatment is ordinarily of a duration not greater than an hour or at most a few hours.

The following examples illustrate the process of the present invention. In these examples, the parts are given as parts by weight, unless otherwise indicated.

Example I Methylcyclopentadiene dimer is gradually added to sodium metal 1526 parts) in diethylene glycol diethyl ether (4313 parts) in a reactor provided with heating means and means to agitate the mixture, the solvent having been previously used in other similar reactions. The total feed of methylcyclopentadiene over a two-hour period is 5870 parts. The reaction is continued for 1 hour at 185 C. and thereafter the temperature is raised to 190 C. for an additional hour to complete the reaction. The reaction mixture is stirred during the entire reaction. Hydrogen gas is evolved and recovered from the reactor. Thereafter, 4410 parts of flaked, anhydrous nickel chloride (97 percentpure) is added to the reaction mixture and the reaction maintained at a temperature of 165 until all evidence of reaction ceases. The mixture is also agitated during this second reaction. The reaction mixture is then transferred to a pressure vessel provided with an agitator and to this second reaction mixture is added nitric oxide at a pressure of p.s.i.g. The total nitric oxide consumed in the reaction is 1200 parts. The reaction is maintained at a temperature of C.

The crude third reaction mixture is then discharged to a vacuum distillation still and the volatile components removed by distillation at a pressure of about 20 millimeters of mercury. The overhead temperature at the end of this vacuum distillation is between 70 and 90 C. When most of the volatile material is removed, 5640 parts of a high boiling hydrocarbon suspending agent, which is predominantly benzene and naphthalene derivatives sold under the trade name ENJAY HB Aromatic Form 9700, marketed by Esso Standard Oil Company, is added to the still. This aromatic mixture has an initial boiling point of about 145 C. at 20 millimeters mercury pressure. The vacuum distillation is continued until no volatile materials were left in the residue.

The impure volatile fraction of the crude reaction mixture is then heated to a temperature of 230 C. under 50 p.s.i.g. pressure and maintained at this temperature for a period of one hour to stabilize the mixture for subsequent separation. This stabilized mixture is then passed into a distillation column having 25 plates. The column is main- .tained at atmospheric pressure. The overhead stream from this column is taken out at a temperature of C. and has the following composition:

Parts Light ends 200 Methylcyclopentadiene 1218 Diethylene glycol diethyl ether 20 Methylcyclopentadienyl nickel nitrosyl 20 Parts Diethylene glycol diethyl ether 4293 Methylcyclopentadienyl nickel nitrosyl 4525 Aromatic suspending agent 3900 This stream is then passed into a second fractionation column operating at about 30 mm. The overhead from this second column contains only about 10 parts of methylcyclopentadiene, 10 parts of diethylene glycol diethyl ether, and about 110 parts of methylcyclopentadienyl nickel nitrosyl. This stream is recycled to the first column. The bottoms from the second column is principally product, methylcyclopentadienyl nickel nitrosyl, diethylene glycol diethyl ether, and the aromatic suspending agent. The bottoms, which consist of 4283 parts of the ether solvent, 4415 parts of methylcyclopentadienyl nickel nitrosyl and 3900 parts of the suspending agent, is passed to a third column, maintained at a pressure of 30 mm. The methylcyclopentadienyl nickel nitrosyl is removed overhead at a temperature of 75-77 C. The bottoms from the third column are passed to a fourth column maintained at atmospheric pressure. in this column the diethylene glycol diethyl ether is removed overhead at l85-190 C. The bottoms from this fourth column, which is principally the aromatic suspending agent, is recycled to the initial distillation still wherein the volatile s ame i S components of the crude reaction mixtures are separated from the inorganic impurities and polymer.

In second and subsequent cycles only about 0.085 part of methylcyclopentadienyl nickel nitrosyl are present in the sodium reaction per part of sodium metal. The recovered yield of methylcyclopentadienyl nickel nitrosyl in each of the cycles discussed above is quite high.

The purified methylcyclopentadienyl nickel nitrosyl compound when mixed with gasoline increases appreciably the octane rating of the gasoline.

The cyclopentadienyl nickel nitrosyl compounds when mixed with gasoline increase appreciably the octane rating of the gasoline. For example, cyclopentadienyl nickel nitrosyl raised the octane number of a toluene-diisobutylene-isooctane-n-heptane fuel from 91.2 to 93.8 at a concentration of 1.0 gram of nickel per gallon and to 95.0 at a concentration of 2.0 grams of nickel per gallon (Research Method, ASTM D-90855).

Example 11 Example I is repeated except that the three chemical reactions are conducted in 6040 parts of diethyl ether instead of diethylene glycol dimethyl ether. The sodium reaction is carried out at 40 C. In this instance, the diethyl ether is removed by distillation prior to the thermal stabilizing treatment of the impure, methylcyclopentadienyl nickel nitrosyl reaction product. Also, the thermal treatment in this instance is conducted at 220 C. for 45 minutes. Upon separation of the polymerized methylcyclopentadiene this monomer is recycled directly to the sodium reaction without dimerization.

Example III Example I'is repeated except that cyclopentadiene is reacted instead of methylcyclopentadiene and the thermal stabilizing treatment is conducted at 240 C. The product is pure cyclopentadienyl nickel nitrosyl.

Example IV Diethylcyclopentadiene is used to form the corresponding nickel nitrosyl product and diethylene glycol methylethyl ether is employed as the solvent. The sodium reaction is conducted at 160 C. In this instance, the thermal stabilization and solvent distillation is conducted simultaneously at the atmospheric boiling point of the solvent. The fractionation procedure is slightly changed, in a manner familiar to those skilled in the art, since in this instance the solvent has a lower boiling point than the product.

Example VI In this run indene is used instead of methylcyclopentadiene to form indenyl nickel nitrosyl. Diethylene glycol dimethyl ether is used as a solvent. The sodium reaction is carried out at 200 C. Similar results are obtained with cyclohexyl amine as the solvent and with aniline as the solvent. The fractionation procedure is s lightly changed, in a manner familiar to those skilled in the art, since in this instance the solvent has a lower boiling point than the product.

Example VII Example I is repeated except that diethylene glycol dibutyl ether is used as a solvent and no aromatic hydrocarbon is employed in the recovery steps.

When the above examples are repeated using other alkali metals such as potassium, lithium, or using other nickel salts such as nickel oxides, nitrates, nitrites, sulfates, sulfites, butyrates, propionates, and the like, similar results are obtained. Likewise when the nickel salt reaction is conducted at temperatures of 180 and 210 C. comparable results are obtained. The nitrosylation reaction is carried out with similar results when nitric oxide pressures of atmospheric, 200, 400 and 1000 p.s.i.g. are employed and when the temperature of the reaction is variable such as using temperatures of 0, 20, 50, 180 and 220 C. When greater quantities of cyclopentadiene dimer are present in the impure reaction product, e.g. when larger excesses of the hydrocarbon are used in the reaction, similar results are obtained. Thus when the reaction products of the above examples is 20, 50 and 100 percent hydrocarbon polymer, based upon the weight of the product, virtually identical results are obtained.

The reaction of sodium and cyclopentadiene or its derivatives can be conducted in ether or amine, solvents at widely varying temperature conditions, generally from about 50 to 300, C. The preferred temperature depends both upon the specific solvent employed and upon the cyclopentadiene hydrocarbon which is reacted with sodium. Some ,of the cyclopentadiene compounds are ditficult to maintain in monomeric form and thus they are more convenient to use in dimeric or low polymeric form. With these compounds, temperatures in the range of to 250 C. are preferred, especially between 180 and C. When monomeric cyclopentadiene compounds are used, temperatures in the range of 100 to 150 C. give best results. Above 100 C. the sodium is in liquid form and thus the system can be merely agitated mildlyto maintain a homogeneous mixture of the sodium and the reaction medium.

Many of the most useful cyclopentadiene hydrocarbons have a relatively low boiling point, at least in their monomeric form. With these hydrocarbons, the feed to the sodium reaction is maintained essentially equivalent to their rate of reaction to prevent vaporization and loss with the evolved hydrogen. It is found, however, that under the conditions of the present invention, excellent reaction rates and yields can be obtained even with the low boiling cyclopentadiene compounds without appreciable loss with the generated hydrogen. The maintenance of a reflux system in the sodium reaction can be used to increase the efficiency of hydrocarbon utilization at the more elevated temperatures.

Ethers and amines are used in the process. Typical examples of ethers are dimethyl ether, methyl ethyl ether, methyl isopropyl ether, n-isopropyl ether or a mixture of these ethers. Polyethers are also suitable in the present invention and include ethylene glycol diethers and polyethylene glycol diethers, the diethylene glycol ethers being preferred. Typical examples are ethylene glycol dimethyl ether, ethylene glycol methyl ethyl ether, ethylene glycolmethyl butyl ether, ethylene glycol butyl lauryl ether and the like. Typical examples of the preferred diethylene glycol diethyl ethers are the dimethyl, ethyl methyl, diethyl, ethyl butyl, dibutyl, and butyl lauryl ethers. Best results are obtained with alkyl groups of from 1 to 6 carbon atoms.

Other suitable ethers are triethylene glycol ethers such as dimethyl, diethyl, methyl ethyl, etc., glycerol ethers such as trimethyl, dimethyl ethyl, diethyl methyl, etc., and cyclic ethers such as dioxane, tetrahydrofuran, methyl glycerol formal and dimethylene pentaderythrite.

A wide variety of amines are suitable for use as solvents in the present invention, including both aliphatic and aromatic amines. Typical examples are dimethyl amine, trimethyl amine, dimethyl ethyl amine, tetramethyl methylene diamine, aniline, methyl aniline, dimethyl aniline, N-methyl morpholino, cyclohexylamine and the like.

The quantity of solvent which can be employed in the sodium reaction, and in the subsequent reaction can vary from about 0.2 part to about parts or more per part of bis(cyclopentadienyl) nickel compound which is formed in the second step of the reaction. The more concentrated recipes are more usually preferred such for example as from about 0.5 to 1.2 mole per mole of reactants. There are many economics involved in the use of a minimum quantity of solvent, particularly in increasing throughput of a unit reaction volume and decreased cost in the separation and recovery of the solvent.

The sodium cyclopentadienyl compound, preferably the reaction product of the first reaction, is then reacted with a nickel salt, either inorganic or organic. Best results are obtained with a nickel halides and particularly the chloride. However, very good results are also obtained with organic salts such as nickel acetate. Many of the nickel salts are hydroscopic and best results are obtained if the salt is maintained in an anhydrous form. Typical examples of suitable n ickel salts are nickel chloride, bromide, iodide, fluoride, nitrate, sulphate, sulphide and various oxides such as NiO and the like. The quantity of nickel salt employed for reaction with the sodium cyclopentadienyl compound is important. Molar quantities of from 0.3 to about 1.5 of nickel salt to sodium cyclopentadienyl compound can be used, although it is best to use a slight excess of nickel salt. Thus from about 1.05 to 2.0 moles of nickel salt should be used per 2 moles of cyclopentadienyl sodium compound.

Higher concentrations of nickel salt can be used when a reducing agent is used in the nitrosylation step, such as a group I-III metal, metal hydride or organo metal compound containing a metal to carbon bond. Under these conditions, an equimolar quantity of cyclopentadienyl sodium and nickel salt is employed.

The temperature of the nickel salt reaction can be from about 50 to 250 C. A more preferred temperature range is from between 100 and 200 C. The pressure of the reaction can be atmospheric or subatmospheric.

Superatmospheric pressures can also be used and is desirable when a low boiling solvent is employed, i.e. solvents which boil below reaction temperature.

In the nitrosylation reaction, nitric oxide pressures of from about atmospheric to about 10,000 -p.s.i.g. can be used. Excellent reaction rates are obtained with pressures of atmospheric to 100 p.s.i.g. nitric oxide pressure.

The temperature of the nitrosylation reaction, as pointed out above, can be conducted at temperatures of from about 0 to 300 C. although the most preferred temperature range is from about 25 to 100 C. Very excellent reaction rates are obtained at temperatures of to C.

We claim:

1. The process of separating a cyclopentadienyl nickel nitrosyl compound from an impure reaction product containing the same and also containing unreacted cyclopentadiene hydrocarbon compound in polymeric form, comprising subjecting said impure product to a temperature above about 1:60 C. for a period of time ranging from 10 minutes to one hour so as to depolymerize said cyclopentadine compound, and thermally stabilize said reaction product, thereafter fractionating said stabilized reaction product to separate cyclopentadine compound from said cyclopentadienyl nickel nitrosyl compound.

2. The process of claim 1 wherein the fractionation and depolymerization steps are combined by conducting the distillation under elevated pressure and at a temperature above C. so as to simultaneously stabilize the mixture and separate its components.

Piper et al.: J. Inorganicand Nuclear Chemistry, vol. I, pages -174. 

1. THE PROCESS OF SEPARATING A CYCLOPENTADIENYL NICKEL NITROSYL COMPOUND FROM AN IMPURE REACTION PRODUCT CONTAINING THE SAME AND ALSO CONTAINING UNREACTED CYCLOPENTADIENE HYDROCARBON COMPOUND IN POLYMERIC FORM, COMPRISIG SUBJECTING SAID IMPURE PRODUCT TO A TEMPERATURE ABOVE ABOUT 160*C. FOR A PERIOD OF TIME RANGING FROM 10 MINUTES TO ONE HOUR SO AS TO DEPOLYMERIZE SAID CYCLOPENTADINE COMPOUND, AND THERMALLY STABILIZE SAID REACTION PRODUCT, THEREAFTER FRACTIONATING SAID STABILIZED REACTION PRODUCT TO SEPARATE CYCLOPENTADINE COMPOUND FROM SAID CYCLOPENTADIENYL NICKEL NITROSYL COMPOUND. 